1. Field of the Invention
The invention relates to a method for manufacturing semiconductors, and in particular to a method for manufacturing an inductor with resonant frequency and Q value increased in semiconductor process.
2. Description of the Prior Art
In the prior art, a spiral metal layer functioning as an inductor is typically formed over a field oxide layer. As shown in FIG. 1, a perspective view shows a structure of an inductor manufactured in semiconductor process according to the prior art, wherein reference numerals 10, 11, 12 and 18 indicate substrate, field oxide, dielectric layer and spiral metal layer, respectively. Even though this structure for manufacturing an inductor is really simply, this inductor formed based on this structure has high substrate coupling effect, resulting in reducing resonant frequency and Q value thereof.
For solving the above-mentioned problem, another method for manufacturing an inductor with high resonant frequency and Q value in semiconductor process is disclosed. As shown in FIG. 2, a structure of another inductor manufactured in semiconductor process according to the prior art is shown, wherein reference numerals 10, 11, 12, 13 and 18 represent substrate, field oxide, dielectric layer, air layer and spiral metal layer, respectively. The air layer 13 formed under the spiral metal layer 18 which serves as an inductor, can reduce substrate coupling effect, and thereby the resonant frequency and Q value of the inductor are raised. Due to the existence of the air layer 13, however, the upper layer, the spiral metal layer 18, cannot obtain an efficient support, causing the spiral metal layer 18 easily to collapse.